1. Field of the Invention
The present invention concerns a bias means of a guide shaft in order to guide the movement of a head unit mainly composed of an optical pick-up of a disk device that drives an optical disk (for instance, CD-R/RW, DVD-R/RW, etc.) as the recording medium for recording a great deal of information in various computer systems and so on, and a recording and playback system built in the computer or audio-visual equipment or diffused as a peripheral unit.
2. Detailed Description of the Prior Art
In general, the PC (hereinafter, it is called PC) cannot lack the disk device for recording/reproduction of information on an optical disk, and so builds it into the PC main body or connects it so called as an external device with the cable.
FIG. 4 shows the externals of a laptop PC with a built-in disk device, and in general, the Disk device D is built into a side of a main body P of the PC, the part of bezel 102 of a disk tray 101 pops out according to the instruction from the switch operation or the PC, and in addition the user of the PC draws out a disk tray 101 and usually loads the optical disk.
In such a disk device D, a turntable 103 fixed to a driving shaft of a spindle motor disposed right under is arranged at the center of the disk tray 101 as shown in FIG. 5, the turntable clamps a center hole of the optical disk so as to transmit the turning force. Moreover, a head unit 104 composed mainly of an optical pickup reciprocates radially in a slit 101a formed in the disk tray for recording and the reproduction information on the optical disk.
Moreover, the disk tray 101 composed like this is guided by a guide rail 105 and is contained in chassis case 106. The bezel 102 of the disk tray 101 usually inserts a tongue piece 102a thereof in the main body of the disk tray, fixes by fitting, and in addition screws if necessary.
Moreover, the recording and playback system, in which the optical disk (for instance, CD-R/RW, DVD-R/RW) that can record a great deal of information, is used as recording medium, is indispensable especially for the PC, and for audio-video equipment, the recording/reproduction of an information is performed using DVD as a recording medium, so the reliability and the durability is highly demanded for the recording and playback system.
FIG. 4 is the one to show the externals of a laptop PC, and a recording and playback system D is built in a side section of a main body P of the PC, to load and unload an optical disk with a disk tray. In general, the mechanism for loading and unloading the disk tray is omitted, because a laptop PC has to compose extremely flatly, and the disk tray loading is operated as the user pushes it by the finger tip.
The recording and playback system adopted for such a laptop PC is composed unitarily as shown in FIG. 6, and this also becomes an extremely flat form. In the same drawing, the symbol 101 is a disk tray, and this disk tray is guided to a guide rail 105 and contained in a chassis case 106.
A turntable 103 fixed to a driving shaft of a spindle motor disposed right under turntable 103 is arranged at the center of the disk tray 101, and a center hole of the optical disk is clamped with this turntable, and the turning force is transmitted. The symbol 104 is a head unit mainly composed of the optical pickup, it moves radially in a slit 101a formed in the disk tray, to record or reproduce information on the optical disk.
In general, the head unit 104 is fixed to a head base 104a, and head base 104a is slidably attached to a guide shaft, and the head base is composed to translate in a lead groove of a screw shaft, in order to enable a radial movement of the head unit in the disk tray 101.
The inclination of an optical axis of the optical pickup, inclination of the spindle motor and, especially, mounting displacement of the guide shaft make it difficult to determine accurately the relative inclination and distance between the optical pickup and the recording face of the optical disk, in case of such composition. The displacement may vary for each finished product, and the attempt to enable the correction of the displacement in the post-processing has been proposed (for instance, Japanese Patent Laid-Open No. 2000-203801).
As shown in FIG. 11, this consists in arranging a guide shaft 109 so as to be fitted by a seat of an adjusting screw 108 screwed in a chassis 112, and in interposing a helical compression spring 110 between this guide shaft and the chassis, for adjusting the height position of the guide shaft 109 biased upward by rotating the adjusting screw 108. Moreover, in FIG. 9, a leaf spring is interposed in place of the helical compression spring, for adjusting similarly the height position of the guide shaft 109 by rotating the adjusting screw 108.
Also, in the disk device composed as shown in FIG. 5, the chassis case 106 constituting the fixed part is attached to the PC main body, while the disk tray 101 constituting the moving part advances and retracts in this chassis case 106. Therefore, the opening of the chassis case 106 faces the sidewall of the PC main body, and a gap G is formed between an opening 106a of the chassis case 106 and a rear end 101a of the disk tray 101, as shown in FIG. 5.
The disk device in the form shown in FIG. 6 a detection switch 108 that detects the retraction momentarily at the time when the disk tray 101 is drawn out from the PC main body by unloading is set in the disk tray 101 as shown in FIG. 6 or is set in a wiring board 107 mounted on the disk tray 101 and the driving state of the disk tray 101 is recognized, or the power supply to a microcomputer of the wiring board mounted on the disk tray is intercepted based on the signal from this detection switch 108, and the system safety of the device has been improved.
However, if the disk tray is drawn out completely as shown in FIG. 5 when the optical disk is set on the disk tray and loaded, the gap G is created as mentioned above. In such a state, the device is susceptible to damage and risks system safety.
That is, for instance, a foreign body such as a piece of paper, etc. might enter the gap G and the detection switch 108 may be operated. When this happens, the disk tray 101 enters the state compulsorily loaded though it is unloaded and a turntable 103 and a head unit 104 will be driven.
The present invention has been devised in order to solve such a problem, to improve system safety even if the disk tray is drawn out from the PC main body and led to a structurally dangerous state, and to prevent the disk tray from erroneous operation.
Moreover, as shown in FIG. 11 and FIG. 12, when the guide shaft is biased upward and the height position is adjusted with the adjusting screw, it is preferable that the bias force is as strong as possible in the range where the guide shaft is not deformed. That is, it becomes an important condition that the head unit may never vibrate due to the spring flexion when vibration is applied to the PC main body and, moreover, the spring force does not decrease as time passes
However, in case of the composition of FIG. 11, it is necessary to increase the turn number of coil of the helical compression spring in order to secure the spring force and, at the same time, satisfactory maintain a stress characteristic, therefore, the helical compression spring becomes lengthy. An increase in the structural thickness of the entire unit provides enough space to interpose the lengthened helical compression spring, but this increase will influence the thinning of the PC main body. In addition, the height position, that becomes the standard of the guide shaft, will be greatly changed, and a corresponding design change is precipitated.
On the other hand, according to the composition of FIG. 12, it is necessary to adopt a leaf spring having a longer spring, in order to secure the spring force and, at the same time, satisfactory stress maintain a characteristic similarly to the case of helical compression spring and, therefore, the size of the entire leaf spring grows, and it becomes disadvantageous for miniaturization. Moreover, because the spring constant is steep, the leaf spring is irregular in bias force, making it difficult to obtain a high reliability.
The present invention offers a bias means that can strongly bias the guide shaft. In addition, it is the aim of the present invention to prevent the structural thickness of the entire unit from growing, especially considering the bias or spring force may not always be functioning, meaning a more efficient design is desired.